Hydrocarbon fluid compatible micronized polymers

ABSTRACT

Micronized polymers suitable for use in fuels and lubricants having a particle size distribution of less than 30 microns obtained from water-soluble solid organic polymers is provided. A water-soluble solid organic polymer having a number average molecular weight in the range of 1000 to 200,000 is subjected to a molecular segmentation in a polar solvent in a polymer to solvent ratio in the range of 1:1 to 1:10 to produce a micronized polymer having a particle size distribution of less than 30 microns.

The present application claims the benefit of U.S. Patent ApplicationNo. 61/553,586, filed Oct. 31, 2011 the entire disclosure of which ishereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to preparation of certain micronizedpolymers useful for use in fuels and lubricants and the micronizedpolymers prepared by such processes.

BACKGROUND OF THE INVENTION

Engine manufactures in developed countries are continuously challengedto improve the fuel economy and performance of vehicles in the marketplace. The original equipment manufacturers for vehicles are beingpressured to meet and exceed the Environmental Protection Agency'sCorporate Average Fuel Economy (CAFE) requirements as well to reduce thevehicles fuel consumption, which in turn would reduce the dependency onimported oil. CAFE is the sales weighted average fuel economy, expressedin miles per gallon (mpg), of a manufacturer's fleet of passenger carsor light trucks with a gross vehicle weight rating (GVWR) of 8,500 lbs.or less, manufactured for sale in the United States, for any given modelyear. Fuel economy is defined as the average mileage traveled by anautomobile per gallon of gasoline (or equivalent amount of other fuel)consumed as measured in accordance with the testing and evaluationprotocol set forth by the Environmental Protection Agency (EPA). Furtherit is important to ensure that any compounds included in such fuel orlubricants used in vehicles are compatible with the fuels and base oilsin order for the fuel and lubricants to function with vehicles withoutnegatively impacting its operability or performance.

For example, modern engine lubricating oil is a complex, highlyengineered mixture, up to 20 percent of which may be special additivesto enhance properties such as viscosity and stability and to reducesludge formation and engine wear. For years antiwear additives forhigh-performance oils such as zinc dialkyldithiophosphate (ZDDP) hasbeen used that work by forming a protective polyphosphate film on engineparts that reduces wear. This film, referred to as a tribofilm orantiwear film (such as polyphosphate, zinc phosphate, zinc sulfide andiron sulfide), is worn away as engine is operated.

SUMMARY OF THE INVENTION

In accordance with certain of its aspects, in one embodiment of thepresent invention provides a process for preparing a micronized polymersuitable for use hydrocarbon fluids such as fuels and lubricantscomprising: (a) providing a water-soluble solid organic polymer having anumber average molecular weight in the range of 1000 to 200,000 in apolar solvent in a polymer to solvent ratio in the range of 1:1 to 1:10to provide a polymer-containing solution; (b) subjecting said polymer toa molecular segmentation to produce a micronized polymer having aparticle size distribution of less than 30 microns.

In another embodiment, the present invention provides a micronizedpolymers prepared by such process, particularly micronized methylcelluloses, micronized N-vinyl pyrrolidone, and micronized poly(acrylicacid) having particle size distribution of less than 30 microns usefulfor as fuel components and lubricant components.

Hydrocarbon fluids comprising such micronized polymers are alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—This figure represents a schematic embodiment of a spray dryingprocess to prepare the fuel compatible micronized polymer.

FIG. 2—This figure represents a schematic embodiment of a sonificationprocess to prepare the fuel compatible micronized polymer.

FIG. 3—This figure represents the particle counting determinationbetween the commercial Methyl Cellulose and the micronizedmethylcellulose in toluene.

DETAILED DESCRIPTION OF THE INVENTION

We have found that by subjecting certain solid water soluble polymers tomolecular segmentation, a micronized polymer that can be readilydispersed in hydrocarbon fluids, such as fuels and lubricants, isobtained.

Commercial solid water soluble polymers typically have in average aparticle size distribution of 36 microns or larger. Solid water solublepolymers are commercially available from Dow Chemical Company,Polysciences, Inc, and Sigma-Aldrich Co. LLC and others. It has beenfound that micronizing water soluble solid organic polymers such as themethyl cellulose to a Sauter mean diameter of less than 30 microns,preferably less than 25 microns, more preferably less than 20 microns,most preferably less than 15 microns, the micronized methyl celluloseprovide polymers dispersable in hydrocarbon fluids such as lubricantsand fuels. Typically, the micronized polymers have a particle sizedistribution in the range of 0.1-30 microns, preferably have a particlesize distribution in the range of about 0.5 to about 25 microns.

The particle size distribution is given herein by the Sauter meandiameter. The Sauter mean diameter is a measure of the mean particlesize per unit surface area. The Sauter mean diameter (also noted as d₃₂)may be calculated from the surface area (A_(p)) and volume (V_(p)) of aparticle, according to the formula:

D ₃₂=6*(V _(p) /A _(p))

Suitable water-soluble solid organic polymer typically have a numberaverage molecular weight of at least 1000, preferably at least 1500,more preferably at least 2000, to at most200,000, more preferably to atmost150,000. In some embodiments, depending on the applications and/orspecific polymers, smaller average molecular weight polymers may bepreferred, such as having an upper number average molecular weight of50,000 or less, 30,000 or less, 25,000 or less, even 20,000 or less, andmay have the lower limit number average molecular weight of 1000 ormore, 1500 or more, or 2000 or more. Examples of water-soluble solidorganic polymers include, for example, methyl cellulose, poly(N-vinylpyrrolidone), and poly (acrylic acid)

Water solubility is defined as having a hydrophilic/lipophilic balance(HLB) equal to seven or greater. The HLB is determined by calculatingvalues for different parts of the molecule, according to the followingequation:

HLB=20*M _(h) /M

Where M_(h) is the molecular weight of the hydrophilic portion of themolecule and M is the molecular mass of the whole molecule.

Suitable polar solvents are water, oxygenated solvents having 1-8 carbonatoms, preferably C1-C4 alcohols, such as for example, methanol,ethanol, propanol, and butanol, C2-C5 ketones, such as for example,methyl ethyl ketone andacetone, C4-C8 ethers such as for example,diethyl ether, dipropyl ether, and dibutyl ether, C2-C5 acids such asfor example, acetic acid, ethanoic acid, propionic acid, butanoic acid,and C3-C7esters such as for example, methyl ethanoate, ethyl ethanoate,butyl ethanoate, methyl propanoate, butyl propanoate and propylbutanoate.

A process where polymer aggregates are de-entangled via processing isreferred to as “Molecular Segmentation”. Molecular Segmentation is aprocess which increases the critical entropy energy of the polymeraggregate by intrapenetrating the polymer aggregate matrix andgenerating/developing a simpler singular Methyl Cellulose polymer. Thisprocess generates a smaller particle size without degrading the polymersmolecular weight. Molecular Segmentation can be generated in a number ofways such as thermally, vibrationally or chemically to name a few.

Examples of methods that can be used for molecular segmentation includespray drying, microfluidization, sonification, pan coating, airsuspension coating, centrifugal extrusion, vibrational nozzle,ionotropic gelation, coacervation, interfacial polycondensation,interfacial crosslinking, in-situ polymerization, electrospinning andmatrix polymerization

As an example, FIG. 1 is a process flow diagram of one embodiment of aprocess to prepare fuel compatible micrnonized polymers. A process flowdiagram of another embodiment is illustrated in FIG. 2.

In reference to FIG. 1, in a schematic flow diagram of one embodiment ofthe invention process 100, the solution containing water-soluble organicpolymer 10 and drying medium 2 are introduced to a two-fluid nozzle 1that is operated by compressed air to disperse the solution containingwater-soluble solid organic polymer 10 into fine droplets to provide adroplet containing micronized polymer. The drying medium 2 (e.g., air)may be electric heated and introduced. The fine droplets are dried tosolid particles in the spray cylinder 3 forming solid particles. Thesolid particles are separated in the cyclone 4, to fine solid particlesin the collection vessel 5 and finer separated solid particles which arepassed to the outlet filter to remove the finer solid particles onto thefilter 6, while flow is generated by an aspirator 7. The solid driedmicronized particles are collected from 5 and 6 (lighter particles thatcannot be separated in the cyclone)

In reference to FIG. 2, in a schematic flow diagram of one embodiment ofthe invention process 200, the solution 22 containing water-solubleorganic polymer 24 is provided to an inlet reservoir 20 where thestarting emulsion/dispersion is provided. The startingemulsion/dispersion is then pass through a high pressure intensifierpump 30 to generate high pressures required for homogenization (typicalpressure range of about 5,000 to about 40,000 psi) thereby generating ahigh pressure solution stream. The high pressure solution stream istypically monitored by a pressure gauge or transducer 40 to set pressure(typically up to 40,000 psi). The high pressure solution stream is thenintroduced to the interaction chamber 50 where the polymer is subjectedto molecular segmentation by splitting the high pressure solution stream52 to a first high pressure split stream (52A) and second high pressuresplit stream (52B) then combining the first and second high pressuresplit stream at 54 to generate molecular segmentation to produce amicronized polymer stream 56. The micronized polymer stream is thencollected 62 at the outlet reservoir 60. Solution is removed from thecollected micronized polymer stream to obtain the micronized polymer.

The water-soluble solid organic polymer subjected to a molecularsegementaion process produces a micronized polymer compatible withhydrocarbon fluids such as fuels and lubricants. Such micronized polymerhave particle size distribution of less than 20 microns, preferably lessthan 25 microns, more preferably less than 20 microns, even morepreferably less than 15 microns, and have a number average molecularweight of at least 1000, preferably at least 1500, more preferably atleast 2000, to at most200,000, more preferably to at most150,000. Insome embodiments, depending on the applications and/or specificpolymers, smaller average molecular weight polymers may be preferred,such as having an upper number average molecular weight of 50,000 orless, 30,000 or less, 25,000 or less, even 20,000 or less, and may havethe lower limit number average molecular weight of 1000 or more, 1500 ormore, or 2000 or more. Examples of such micronized polymers include, forexample, micronized methyl cellulose, micronized poly(N-vinylpyrrolidone), and micronized poly (acrylic acid). The micronized polymermay have a particle size distribution of at least 0.1 microns,preferably at least 0.5 microns.

It was found that while the non-micronized polymer does not readilydisperse in hydrocarbon fluids, the micronized polymer readily dispersesin such hydrocarbon fluids. As such hydrocarbon fluids, such as fuelsand lubricants, containing the micronized polymer dispersed in thehydrocarbon fluids may be obtained. The primary method used to assessdispersion stability is zeta potential. The zeta potential is thepotential difference between the dispersing medium and the stationarylayer of fluid interacting with the dispersed particle. The significanceof zeta potential is that this value can be related to the stability ofcolloidal dispersions. The zeta potential indicates the degree ofrepulsion between adjacent, similarly charged particles in a dispersion.Colloids with high zeta potentials are electrically stabilized, and willresist aggregation, while colloids with low zeta potentials willcoagulate or flocculate. This is especially important in fuel andlubricant applications, as polar polymers are not soluble in thesemedia. Therefore, micronization may be employed to improve the stabilityof adding these materials to fuels and lubricants, and the degree ofimprovement may be monitored by zeta potential.

Generally, the micronized polymers are added to a hydrocarbon fluid inan amount in the range from about 0.001% by weight, to about 10% byweight based on the total weight of the hydrocarbon fluid to produce thehydrocarbon fluid containing the micronized polymer. The amount of themicronized polymers added may vary based on the application and/or thespecific micronized polymer. In some embodiment depending on theapplication and/or the micronized polymer, an amount in the range fromabout 0.01% by weight to about 1% by weight, based on the hydrocarbonfluid may be added to produce the hydrocarbon fluid containing themicronized polymer.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexamples herein described in detail. It should be understood, that thedetailed description thereto are not intended to limit the invention tothe particular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention as defined by the appendedclaims. The present invention will be illustrated by the followingillustrative embodiment, which is provided for illustration only and isnot to be construed as limiting the claimed invention in any way.

ILLUSTRATIVE EMBODIMENT Test Methods Average Particle Counting

The particle sizes were determined using a laser-based particlecounting/sizing system developed by Spectrex Corporation, model PC-2200.This system uses a laser diode operating at 650 nm to achieve particlecounting and sizing through the scattering of the resultant light. Thelight is focused onto a 2 cm segment of the sample stream, and thephotodetector is positioned to measure light scatter in the near-forwarddirection of the sample over an angle between 4° and 19°. Thephotodetector is gated to only allow sizing of in-focus particles, asout of focus particles will produce broadened pulses, which can beremoved from the analysis. Typical accuracy of a single passcounting/sizing run is +/−15%, which can be minimized further throughsuccessive runs. The samples were measured as dispersions in toluene,with an opacity below 30%.

Average Particle Size (Particle Size Distribution)

A Malvern Mastersizer 2000 outfitted with a Sirocco dry powder accessorywas used for the determination of average particle size. An adequateamount of sample is placed within the Sirocco accessory, and thematerial is then fed into the measuring unit (Mastersizer 2000) using anultrasonics setting of approximately 50% (to provide a reasonablematerial feed rate). The critical parameter to be adjusted during thismeasurement is the air pressure. Since water-soluble polymers absorbmoisture well, they often agglomerate easily when not dispersed in asolvent. Therefore, air is used to assist in breaking up theseagglomerations. The air pressure is titrated to provide the bestmeasurement conditions. To compare micronized polymer with thecommercial starting material, the Sauter mean diameter is used.

Density (ASTM D70)

The density of the solid was measured using a calibrated pyconometer.The pycnometer and sample are weighed, then the remaining volume isfilled with helium. The filled pycnometer is brought to the testtemperature, weighed. The density of the sample is calculated from itsmass and the mass of helium displaced by the sample in the filledpycnometer.

Zeta Potential

The Malvern Nano-Z is designed to measure zeta potential using laserlight scattering. The process involves placing a sample of appropriateconcentration (0.1% to 15%, depending on the light absorbancecharacteristics of the material) in a “dip cell”, which consists of acuvette equipped with electrodes to place a potential across the sample.The instrument is automated with respect to the measurement process, andself-adjusts the settings to optimize the results. The zeta potentialwas measured in water.

Molecular Weight

A gel permeation chromatograph (GPC) was used to determine the molecularweight of each sample. Calibration was achieved using dextran/pullulanstandards. The eluent was 0.1M sodium nitrate in water or 0.1M sodiumnitrate in water with 20% methanol. The precolumn was a PSS Suprema 10micron, 30 Å, ID 8×50 mm. Three columns were used: PSS Suprema 10micron, 100 Å, ID 8×300 mm, PSS Suprema 7 micron, 300 Å, ID 8×300 mm,and PSS Suprema 10 micron, 1000 Å, ID 8×300 mm. The flow rate was 1.0mL/min. The sample concentration was 2.0 g/L and the measurementtemperature was 23° C. Detection was provided by PSS SECcurity UV-VIS @230 nm and PSS SECcurity RID. Calculations were performed using PSSWinGPC Unity Ver. 8.0 software.

Molecular Segmentation Process

Micronized methyl celluloses were prepared using Methocel E4M and A15LVpremium hydroxylpropyl methylcellulose obtained from Dow ChemicalCompany. Micronized poly (N-vinyl pyrrolidone) were prepared using poly(N-vinyl pyrrolidone) obtained from Polysciences, Inc. Micronizedpoly(acrylic acid) were prepared using poly(acrylic acid) obtained fromSigma-Aldrich Co. LLC.

Spray Dry Method.

The micronized polymers were prepared using Buchi Model B-290 SprayDrier under the following conditions.

Solution Preparation: a 3% polymer/DI water solution is left to stirovernight.

Spray Dyer Settings: Buchi B-290 Temperature: 110° C. Aspirator: 100%Air Flow: 600 L/hr Pump Rate: 35%

Once the inlet temperature reaches the set temperature (110° C.), thepolymer/water solution is fed at a 35% pump rate. Once all the solutionhas been dried, the receiving container is opened and the dried finalproduct is then collected.

The Sauter mean diameter of the methyl cellulose before and after themicronization process, measured according to the test method describedabove, is provided below (in microns).

Commercial Methyl Cellulose: 59.4 Micronized Methyl Cellulose 7.5

FIG. 3 show that the micronization process reduces the size of theparticles of the commercial Methyl Cellulose from 100 microns to below30 microns in size in toluene solution by particle counting.

The density of the methyl cellulose before and after the micronizationprocess measured, according to the method described above, is providedbelow.

Commercial Methyl Cellulose  1.456 g/cm³ Micronized Methyl Cellulose1.6802 g/cm³

The molecular weight of the polymer remains substantially unchanged, asshown below for methylcellulose.

Commercial Methyl Cellulose 154,000 g/mol (20% MeOH), 135,000 g/mol (noMeOH) Micronized Methyl Cellulose 143,000 g/mol (20% MeOH) 143,000 g/mol(no MeOH)

The properties of the starting water-soluble solid organic polymers andthe micronized solid organic polymers prepared according to the methodabove are provided below in Table 1.

TABLE 1 Sauter Mean Zeta Diameter Surface Area Potential Density VolumeSample (microns) (m²/g) (mV) (g/cm3) (cm3) HLB MW poly(N-vinyl 36.30.116 −6.51 1.2197 1.0333 17.7 3,780 pyrrolidone) micronized 10.2 0.415−9.73 1.2271 1.0185 17.7 3,450 poly(N-vinyl pyrrolidone) poly(acrylic78.7 0.0725 −3.39 1.3965 0.4793 12 13,800 acid) micronized 6.2 0.916−13.8 1.431 0.5012 12 14,000 poly(acrylic acid) methyl 59.4 0.0998 −4.581.456 0.3422 18 154,000 cellulose micronized 7.5 0.789 −7.3 1.68020.1084 18 143,000 methyl cellulose

Microfluidization Method

The micronized polymers were prepared using Microfluidics M-110Pmicrofluidizer under the following conditions.

Solution Preparation:

0.1%-3% polymer/DI water/hydrocarbon mixture (55%-99% xylenes)/0.1%-15%(based on total volume) surfactant. (The hydrocarbon preferably has aboiling point greater than 100° C.)

Emulsion Preparation Process

a. the polymer/DI water and surfactant mixture is processed through aRoss mixer (or similar) for 3-4 minutes at low speed (500-4,000 RPM).

b. The preprocess mixture is added to a hydrocarbon. The amount ofhydrocarbon is greater than the amount of DI water added. The resultingsolution is once again processed in the Ross mixer for 5-8 minutes atlow to moderate speed (1,000-5,000 RPM).

c. The resulting polymer/DI water/surfactant and hydrocarbon emulsion isprocessed 1 or more times via the microfluidics equipment to achieve thedesired droplet size, this is typically accomplished in 3 passes.

d. The final stage of the process is to dry the final polymer/DIwater/surfactant/hydrocarbon blend in a rotary-evaporator (or othersolvent removal method, such as freeze-drying) to remove the water andhydrocarbon to produce a very fine powder. (removal of the hydrocarbonsolvent is optional)

What is claimed is:
 1. A process for preparing a micronized polymersuitable for use in fuels and lubricants comprising: (a) providing awater-soluble solid organic polymer having a number average molecularweight in the range of 1000 to 200,000 in a polar solvent in a polymerto solvent ratio in the range of 1:1 to 1:10 to provide apolymer-containing solution; and (b) subjecting said polymer tomolecular segmentation to produce a micronized polymer having a particlesize distribution of less than 30 microns.
 2. The method of claim 1wherein the micronized polymer has a particle size distribution of 25microns or less.
 3. The method of claim 1 wherein the molecularsegmentation is by spray drying.
 4. The method of claim 1 wherein themolecular segmentation is by microfluidization.
 5. The method of claim 4wherein the solvent is removed from the micronized polymer.
 6. Themethod of claim 1 wherein the polymer is subjected to molecularsegmentation to produce a micronized polymer having a particle sizedistribution of less than 20 microns.
 7. The method of claim 1 whereinthe polymer is subjected to molecular segmentation to produce amicronized polymer having a particle size distribution of less than 15microns.
 8. The method of claim 1 wherein the water-soluble solidorganic polymer is a methyl cellulose.
 9. The method of claim 1 whereinthe water-soluble solid organic polymer is a poly (N-vinyl pyrrolidone).10. The method of claim 1 wherein the water-soluble solid organicpolymer is a poly(acrylic acid).
 11. A micronized polymer of awater-soluble solid organic polymer having number average molecularweight in the range of 1000 to200,000 and a particle size distributionof less than 30 microns.
 12. The micronized polymer of claim 11 whereinthe particle size distribution is 25 microns or less.
 13. The micronizedpolymer of claim 12 wherein the micronized polymer is a micronizedmethyl cellulose.
 14. The micronized polymer of claim 12 wherein themicronized polymer is a micronized N-vinyl pyrrolidone.
 15. Themicronized polymer of claim 12 wherein the micronized polymer is amicronized poly (acrylic acid).
 16. The micronized polymer of claim 11wherein the particle size distribution is 20 microns or less.
 17. Themicronized polymer of claim 11 wherein the particle size distribution is15 microns or less.
 18. A hydrocarbon fluid comprising the micronizedpolymer of claim
 11. 19. The hydrocarbon fluid of claim 18 wherein themicronized polymer is a micronized methyl cellulose.
 20. The hydrocarbonfluid of claim 18 wherein the micronized polymer is a micronized N-vinylpyrrolidone.
 21. The hycrocarbon fluid of claim 18 wherein themicronized polymer is a micronized poly (acrylic acid)
 22. A hydrocarbonfluid comprising the micronized polymer of claim 12.